1. Field of the Invention
The invention relates to methods, ultrasound probes, and instrumentation for real time 3D imaging around the tip of an ultrasound probe that can be inserted into the body, either through natural openings or through surgical wounds.
2. Description of the Related Art
Real time (Rt) three-dimensional (3D) ultrasound imaging around the tip of a flexible ultrasound probe is in many situations a sought after tool, both for diagnosis and for guidance of procedures. Examples of such procedures are placement of devices in the heart ventricles and atria, guidance of electrophysiology ablation, or guidance in minimal invasive surgery. In these cases, the ultrasound probe gets in direct contact with the blood path, and it is then a great advantage to use factory-sterilized, disposable probes. This requires that the manufacturing cost of the probes can be kept low.
Such 3D imaging around a probe tip is done by scanning a pulsed ultrasound beam in the two angular directions in front of the probe. This type of scanning is ideally done with a two-dimensional matrix array where the element width is less than λ/2 in both directions, where λ is the wave-length of the ultrasound in the tissue. However this gives a large amount of small elements, that either requires an impractically thick cable connecting the array and the instrument, or requires a large amount of beam forming electronics at the probe tip close to the array, which is expensive and space consuming to be used with probes that are inserted into the body. The small size of the elements of the matrix probe also makes it difficult to manufacture the matrix arrays for ultrasound frequencies above 7 MHz.
There is further a need for the probe to be flexible, for example for insertion into the vessels and the heart as a catheter. In this situation one could also want to control flexing of the tip from the external instrument. In other situations, like endoscopic surgery, one would like to have a stiff probe.